speed of light

Originally posted by son of godzilla
re-time travel.
Being a reptile I deem my heartbeat to be my absolute clock. If I indulged
in space travel my heartbeat would remain constant but human clocks would
vary as stated in other posters.

Wow, you can DEEM yourself to be independent of relativity. Impressive!

Originally posted by KellyJay
In theory.
Kelly

not so fast, he forgot to factor-in time spent turning his ship around 😉

Originally posted by O Artem O
well this dosen't have to do with time but if you are traveling in a space ship close to the speed of light your space ship and every thing in it get smaller. if you are traveling a couple of miles below the speed of light you will almost be flat!!! there is also a formula for this if your interested

I thought if you traveled close to the speed of light, you would begin to gain mass. I thought this was the basis for E = M x C(squared). I also think some folks have their point of reference mixed up.

If you travel to a place two light years distant at the speed of light, you will arrive there in two years. However, because you were traveling at the speed of light, it will appear to you, looking back at the Earth, as if time stood still on Earth while you were traveling. However, on Earth you will appear to have moved at half the speed you were actually traveling until you get there. The sight of you on Earth after you had been traveling for one year, will not arrive at Earth for another year. You will appear to have covered one light years distance in two years. It is the point of reference that causes most of the effects of time distortion. Time is not distorted, but your perception would be distorted.

Originally posted by dinosaurus
I thought if you traveled close to the speed of light, you would begin to gain mass. I thought this was the basis for E = M x C(squared). I also think some folks have their point of reference mixed up.

If you travel to a place two light years distant at the speed of light, you will arrive there in two years. However, because you were traveling at th ...[text shortened]... the effects of time distortion. Time is not distorted, but your perception would be distorted.

I cant make sense of what you are saying. However, I can assure you that time is most definitely distorted and as was pointed out earlier in this thread, GPS would not work if we didn't take that fact into account. Clocks on satellites go measurably slower than clocks on the surface of the earth.

Originally posted by dinosaurus
If you travel to a place two light years distant at the speed of light, you will arrive there in two years. ...

I can go wherever I want in Universe, in near to no time at all, if I only have the technology to do it (which I don't).

As an example: I can go to Alpha Centauri in five minutes, if I look at my wristwatch, turn and go back in another five minutes, and only be 10 minutes older than I were befor this trip. But on Earth, they would have waited for me in two times 4,37 years (The distant to alpha Centauri is 4.37 LightYears.) if they look at their watch.

So how long will my trip take? It depends of what time frame you use. Mine or the stationary others.

Originally posted by shavixmir
No.

Say the distance from point A to point B is a light year.
If you travel from point A to point B in 2 seconds and then take 2 seconds coming back, you will have been gone 4 seconds.

However, since you traveled a light year going and a light year coming back, Point A will be two years, minus 4 seconds further on.

if A and B are a light year apart, then it would take light travelling in a vacuum a year to reach A from B, and another year to make the return journey. if you take two seconds (by your on-ship clock) to make each leg of the journey, then you have travelled at many, many times the speed of light in a vacuum (c). Relativity theory doesn't forbid faster-than-light travel, only travel AT the speed of light. so, yes, perhaps this is possible. however, relativity seems to predict that, for anything travelling faster than c, time would actually not just slow, but move backwards. it has been postulated that there are particles, called tachyons, that travel faster than c, but as far as i know, there has been no experimental verification of their existence.

to answer the original question, yes. if you got on a spaceship and travelled around at, say 0.95c, you would find that more time had elapsed on Earth than had done aboard your ship. if you had left a twin sibling on Earth, you twin would now have aged more than you.

Originally posted by twhitehead
I cant make sense of what you are saying. However, I can assure you that time is most definitely distorted and as was pointed out earlier in this thread, GPS would not work if we didn't take that fact into account. Clocks on satellites go measurably slower than clocks on the surface of the earth.

presumably because the satellites are on a slightly larger diameter orbit

i dont understand why an object could not travel faster than light any speed, is it not a simply a function of force x mass, in a vacuum, if there is no theoretical limit to the force? i guess if it broke the light barrier there might be a flash and we would'nt be able to see it?
we might think it had exploded and was gone.......

Originally posted by eamon o
i dont understand why an object could not travel faster than light any speed, is it not a simply a function of force x mass, in a vacuum, if there is no theoretical limit to the force? i guess if it broke the light barrier there might be a flash and we would'nt be able to see it?
we might think it had exploded and was gone.......

It would take an infinite amount of energy to accelerate an object with mass to light speed.

Originally posted by Iron Monkey
if A and B are a light year apart, then it would take light travelling in a vacuum a year to reach A from B, and another year to make the return journey. if you take two seconds (by your on-ship clock) to make each leg of the journey, then you have travelled at many, many times the speed of light in a vacuum (c).

You have got confused about the fact that the clocks are relative. It takes light a year to travel a light-year as measured by a stationary clock. As measured by the light it takes no time at all. As you accelerate your time slows down relative to stationary clocks.

Originally posted by twhitehead
You have got confused about the fact that the clocks are relative. It takes light a year to travel a light-year as measured by a stationary clock. As measured by the light it takes no time at all. As you accelerate your time slows down relative to stationary clocks.

it true that i didn't explicitly say that the measurement of the time it takes for the light to make the journey is done on a clock stationary relative to the observer on Earth. perhaps to make the point i wanted to make i probably should also have stipulated that the two seconds of the spaceship journey is measured on a clock stationary relative to the observer on Earth, but Shav left this open. there is no such thing as stationary simpliciter, but only stationary relative to some reference frame.

Originally posted by FabianFnas
I can go wherever I want in Universe, in near to no time at all, if I only have the technology to do it (which I don't).

As an example: I can go to Alpha Centauri in five minutes, if I look at my wristwatch, turn and go back in another five minutes, and only be 10 minutes older than I were befor this trip. But on Earth, they would have waited for me in ...[text shortened]... w long will my trip take? It depends of what time frame you use. Mine or the stationary others.

That represents a time dilation of almost 500,000 to 1. That would be tricky to get to the velocity so close to C in such a short distance of 4 LY. If you had the thrust available, you might do it for a distance of a few thousand LY. That must be within one millimeter per second of the speed of light!

Originally posted by Iron Monkey
it true that i didn't explicitly say that the measurement of the time it takes for the light to make the journey is done on a clock stationary relative to the observer on Earth. perhaps to make the point i wanted to make i probably should also have stipulated that the two seconds of the spaceship journey is measured on a clock stationary relative to the ...[text shortened]... h thing as stationary simpliciter, but only stationary relative to some reference frame.

You did in fact specify that the clock was on the spaceship. You said "by your on-ship clock".

Originally posted by sonhouse
That represents a time dilation of almost 500,000 to 1. That would be tricky to get to the velocity so close to C in such a short distance of 4 LY. If you had the thrust available, you might do it for a distance of a few thousand LY. That must be within one millimeter per second of the speed of light!

That is of course why we have not yet sent a spaceship to nearby stars. We could design a spaceship that could attain near light speed, but accelerating it to that speed takes too long, and half-way there you have to start decelerating again!

Originally posted by Nemesio
What reason do you have to doubt this, KellyJay? This 'in theory' business of yours is pretty
tiresome. Since we can prove the formula up until the speeds we can achieve, and since the
formula regarding the 'loss of time' is dead accurate up until that point -- that is the practice
follows the theory -- what on earth would lead you to suspect that somehow for some unexplained
reason that it would not be accurate in fact?

Nemesio

You have done that in practice? Simple question yes or no, if you
have not and cannot and others are all in the same boat than you
and they have to say in theory, you might imagine it is the reality we
live in, but beyond that you are steep in theory nothing more.
Kelly